The myelencephalon or afterbrain is the most posterior region of the embryonic hindbrain, from which the medulla oblongata develops.

Development

Neural tube to myelencephalon

During fetal development, divisions of the

neural tube In the developing chordate (including vertebrates), the neural tube is the embryonic precursor to the central nervous system, which is made up of the brain and spinal cord. The neural groove gradually deepens as the neural fold become elevated, ...

that give rise to the hindbrain (

rhombencephalon The hindbrain or rhombencephalon or lower brain is a developmental categorization of portions of the central nervous system in vertebrates. It includes the medulla, pons, and cerebellum. Together they support vital bodily processes. Metencephal ...

) and the other primary vesicles (

forebrain In the anatomy of the brain of vertebrates, the forebrain or prosencephalon is the rostral (forward-most) portion of the brain. The forebrain (prosencephalon), the midbrain (mesencephalon), and hindbrain (rhombencephalon) are the three primary ...

and

midbrain The midbrain or mesencephalon is the forward-most portion of the brainstem and is associated with vision, hearing, motor control, sleep and wakefulness, arousal (alertness), and temperature regulation. The name comes from the Greek ''mesos'', " ...

) occur at just 28 days after conception. With the exception of the midbrain, these primary vesicles undergo further differentiation at 5 weeks after conception to form the myelencephalon and the other secondary vesicles.

Myelencephalon to medulla

Final shape differentiation of the myelencephalon into the medulla oblongata can be observed at 20 weeks gestation.Carlson, Neil R. Foundations of Behavioral Neuroscience.63-65 1302 Brain Vesicle DevN

Medulla oblongata

The medulla oblongata is part of the brain stem that serves as the connection of the spinal cord to the brain. It is situated between the

pons The pons (from Latin , "bridge") is part of the brainstem that in humans and other bipeds lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum. The pons is also called the pons Varolii ("bridge of Va ...

and the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...

Function

The medulla oblongata is responsible for several functions of the autonomic nervous system. These functions include: 1) Respiration: monitors the acidity of the blood and sends electrical signals to intercostal muscle tissue to increase their contraction rate in order to oxygenate the blood as needed. 2) Cardiac & Vasomotor Center: monitors and regulates cardiovascular activities by: * Sympathetic excitation in order to increase cardiac output * Parasympathetic inhibition of cardiac output * Affecting blood pressure via

vasodilation Vasodilation is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. The process is the opposite of vasoconstrictio ...

and

vasoconstriction Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vess ...

3) Reflexes * Coughing * Sneezing * Swallowing (palatal) * Vomiting * Gagging (pharyngeal) * Jaw jerk (masseter)

Damage/trauma

Because of its location in the brainstem and its many important roles in the autonomic nervous system, damage to the medulla oblongata is usually fatal.

References

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